Treatment of wells



- July 1, 1941- c. F. PRUTTON TREATMENT OF WELLS Filed June 9, 1938 INVENTOR. 62d f Prwfon VL ATTORNEYS.

Patented. July 1, 1941 TREATMENT OF WELLS Carl F. Prutton, Cleveland, Ohio, assignor to The Dow Chemical Company, Midland, Mich, a

corporation of Michigan Application June 9, 1938, Serial No. 212,769

1 Claim. (CL 166-21) My invention relates to an improved method of lining well bores. It more particularly concerns a method of providing a perforated liner for the productive portion of a well bore.

In conventional well drilling practice, it is customary to lower the casing string into the well bore to a point above the producing formation and cement it in place. The well is then produced in the usiial manner, as by pumping. Recently, however, it has been the. practice in some fields to extend the casing through the producing formationto the bottom of the well bore in order to guard against sloughing of the walls of the bore and to prevent the infiltration'of water or brine from contiguous formations. Cement is then forced up around the casing to hold it in place. To produce a well equipped in this manner it is necessary to perforate both the casing and surrounding cement liner to allow the fluid from the producing formation to enter the well bore. This is done by lowering a gun perforator of conventional type into the well through the casing to a point opposite that section of the formation to be opened to production and discharging the steel projectiles from the gunthrough the casing and cement liner into the producing formation This method has the decided disadvantage that the projectiles from the gun perforator penetrate only a relatively short distance, if at all, into the producing formation, it'being necessary for them to first pas through both the casing and surrounding cement before they can reach said formation. A still further disadvantage lies in the fact that perforations made in the conventional cement liner sometimes become clogged or entirely plugged up due to cracking or crumbling of the cement resulting from the shattering action of the projectiles, thus preventing the inflow of clean oil into the well. Frequently these holes become so clogged thatthe inflow of oil is entirely shut ofi. In addition, the cracks produced in the cement liner near both the top and bottom of the perforated portions may permit infiltration when these portions are contiguous to water bearing formations.

One of the objects of my invention is to provide an improved liner for the productive stratum of a well bore.

Another object is to provide a lining for a producing formation which is capable of being easily and cleanly perforated to open the formation to production.

Still further objects and. advantages of the invention will be apparent as the description of the invention proceeds.

Briefly, the invention comprises casing a, well with metal pipe down through the producing formation, and thereafter forcing a. resin-forming liquid up around the. casing to a height just above the producing formation. The annular space between the casing and the well bore, as well as the formation immediately adjacent the bore, is thus impregnated with the resin-forming liquid which is allowed to solidify. The well is then openedto production by perforating the casing and the solidified resin behind the casing.

The invention, then, consists of the method hereinafter fully described and particularly pointed outin the claims, reference being made to the accompanying drawing showing a preferred mode of carrying out the invention'in a through the casing a quantity of a resin-forming well bore. Variations of. the method described may-be employed without departing from the scope of the invention.

The single figure illustrates in vertical section a well bore suitably equipped for carrying out .the invention. As shown, the well bore I is cased with metal pipe 2, which passes through non-productive eanth and rock strata and ends in'productive stratum 3, the metal casing being seated adjacent the'lower level of the production stratum at point 4. The annular space 5 between the metal casing and the well bore is shown filled with solidified resin 6, which has been forced up around the casing 2 and into the formation while in liquid form. The solidified resin 6 is shown filling the annular space and impreg hating the producing formation up to a point I. A gun perforator 8, equipped with a series of leterally directed sockets 9, and fuse lead in attached thereto and to an electrical device above the ground (not shown) for firing bulletsf'or projectiles from the sockets, is shown suspended on cable ii in the well bore opposite the resinimpregnated producing formation 3. Formation 3 is also shown perforated at points l2 by projectiles fired from the gun perforator.

In carrying out the invention in a well cased with metal pipe through the producing formation, I introduce into the lower portion of the bore liquid in amount sufficient to fill the well bore up to a point 1 above the producing formation. Pressure is then applied to the resin-forming liquid, if necessary, to displace it from the well bore into the annular space between the well bore and casing to force it a short distance, if desired, into the surrounding formation 3, where it acts to consolidate the walls ofthe bore after solidification. The resin forming liquid is then allowed to solidify, generally from 2-48 hours being required, depending upon the type of resin forming liquid employed. The extent of the res in support thus formed in the well bore may vary in thickness over relatively wide limits, depending upon the extent to which the resin forming liquid impregnates the surrounding formation. The gun perforator is then lowered into the well bore I to a point opposite the producing formation and discharged. Projectiles are fired through the casing and surrounding resin into formation 3, forming holes 12 to open the bore to production. These holes [2 made by the proiectiles are exceptionally clean, because substantially no shattering of the surrounding resin occurs laterally from the perforations. The perforations thus permit the ready flow of clean oil into the well. In addition, the resin surrounding the perforations does not crumble or crack as does the conventional cement liner and cement impregnated formation.

Suitable resin forming liquids for use in my invention must be insoluble in oil and, if the well is to be later acidized, they should also be insoluble in acid. Also, they must be capable of forming a strong, impermeable sheath when allowed to set in the well bore.

The following are examples showing various resin forming liquids which are suitable for use in carrying out my invention.

Example 1 Mix together 60 parts of unpolymerized styrene, 80 parts of oil pitch, and parts of petroleum oil, and then add a suitable catalyst in amount such that transformation of the liquid mixture into a solid resin will occur after a predetermined time. Stannic chloride may be used for this purpose, the amount selected being suflicient to bring. about polymerization at a convenient rate. The addition of about 1-4 per cent of stannic chloride by volume, based on the volume of styrene used, makes a liquid mixture which is quite fluid and remains so for about 90 minutes at ordinary temperatures. The mixture becomes a strong resinous solid, insoluble in oil, water,

or hydrochloric acid, within 10 hours.

Example 2 Unpolymerized or monomeric styrene may be used undiluted or without a catalyst when the temperature of the well at the point containing the resin forming liquid is high enough to cause polymerization. At 150 F. the mixture becomes a solid resin within '7 days.

Example 3 Mix together 70 parts of liquid vinylidene chlo- Example 4 Petroleum oil is mixed with unpolymerized styrene in amount up to about 30 per cent by volume and about 2 per cent of stannic chloride based on the volume of styrene is added. The function of the petroleum oil is to act as a diluent reducing the speed of reaction, When no oil is added, the mixture of styrene and catalyst alone becomes polymerized in about 2 hours at 100 F. When about 30 per; cent of oil is incorporated in the mixture it becomes semi-solid in about 18 hours and becomes quite solid in about 30 hours.

Example 5 Mix together 80 parts of unpolymerized styrene and 20 parts of hexachloro-diphenyloxide, and about 1.6 per cent of stannic chloride, based on the volume of styrene used. Such a mixture has a specific gravity of about 1.15 and will polymerize into a resinous solid in about 16 hours at 100 F.

The foregoing examples'are merely illustrative .of several resin forming liquids which may be used according to my invention, but other resin forming liquids, e. g. partially condensed phenolformaldehyde mixtures, vinyl chloride or vinyl esters, such as vinyl acetate, etc., may be employed similarly according to my invention.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the steps stated by the following claim or the equivalent of such stated steps be employed.

I therefore particularly point out and distinctly claim asmy invention:

In a method of providing a perforated lining for the bore of a well penetrating a fluid producing formation, the steps which consist in setting a metal casing in the well bore through the productive portion of the formation, introducing sufficient resin forming liquid into the well bore to cover the producing formation, applying pressure to said resin forming liquid to displace it from the well bore and force it up around the casing to fill the annular space between the casi ing and the walls of the bore, maintaining pressure upon said resin forming liquid until it has solidified thereby sealing the casing in place, and then perforating the casing and solidified resin to permit the passage of fluid through the so formed perforations to the well.

CARL F. PRUTTON. 

